flutter屏幕尺寸适配和字体大小适配的实现

dependencies:
 flutter:
  sdk: flutter
 # 添加依赖
 flutter_screenutil: ^0.4.2

import 'package:flutter_screenutil/flutter_screenutil.dart';

//设置适配尺寸 (填入设计稿中设备的屏幕尺寸) 假如设计稿是按iPhone6的尺寸设计的(iPhone6 750*1334)
  ScreenUtil.instance = ScreenUtil(width: 750, height: 1334)..init(context);

//长方形:
Container(
      width: ScreenUtil().setWidth(375),
      height: ScreenUtil().setHeight(200),
      ),
      
//如果你想显示一个正方形:
Container(
      width: ScreenUtil().setWidth(300),
      height: ScreenUtil().setWidth(300),
      ),

   ScreenUtil().setSp(28)     //传入字体大小，根据系统的“字体大小”辅助选项来进行缩放
   ScreenUtil().setSp(28，false) //传入字体大小，不会根据系统的“字体大小”辅助选项来进行缩放

for example:
    Text(
       'My font size is 28px and will not change with the system.',
         style: TextStyle(
          color: Colors.black,
          fontSize: ScreenUtil().setSp(28, false) 
         )
       ),

  ScreenUtil.pixelRatio    //设备的像素密度
  ScreenUtil.screenWidth   //设备宽度
  ScreenUtil.screenHeight   //设备高度
  ScreenUtil.bottomBarHeight //底部安全区距离，适用于全面屏下面有按键的
  ScreenUtil.statusBarHeight //状态栏高度 刘海屏会更高 单位px
  ScreenUtil.textScaleFactory //系统字体缩放比例
  
  ScreenUtil().scaleWidth // 实际宽度的dp与设计稿px的比例
  ScreenUtil().scaleHeight // 实际高度的dp与设计稿px的比例

//导入
import 'package:flutter_screenutil/flutter_screenutil.dart';

...

 @override
 Widget build(BuildContext context) {
  //设置适配尺寸 (填入设计稿中设备的屏幕尺寸) 假如设计稿是按iPhone6的尺寸设计的(iPhone6 750*1334)
  ScreenUtil.instance = ScreenUtil(width: 750, height: 1334)..init(context);
  print('设备宽度:${ScreenUtil.screenWidth}'); //Device width
  print('设备高度:${ScreenUtil.screenHeight}'); //Device height
  print('设备的像素密度:${ScreenUtil.pixelRatio}'); //Device pixel density
  print(
    '底部安全区距离:${ScreenUtil.bottomBarHeight}'); //Bottom safe zone distance，suitable for buttons with full screen
  print(
    '状态栏高度:${ScreenUtil.statusBarHeight}px'); //Status bar height , Notch will be higher Unit px

  print('实际宽度的dp与设计稿px的比例:${ScreenUtil().scaleWidth}');
  print('实际高度的dp与设计稿px的比例:${ScreenUtil().scaleHeight}');

  print(
    '宽度和字体相对于设计稿放大的比例:${ScreenUtil().scaleWidth * ScreenUtil.pixelRatio}'); 
  print(
    '高度相对于设计稿放大的比例:${ScreenUtil().scaleHeight * ScreenUtil.pixelRatio}'); 
  print('系统的字体缩放比例:${ScreenUtil.textScaleFactory}');

  return new Scaffold(
   appBar: new AppBar(
    title: new Text(widget.title),
   ),
   body: new Center(
    child: Column(
     crossAxisAlignment: CrossAxisAlignment.center,
     children: [
      Row(
       children: [
        Container(
         width: ScreenUtil().setWidth(375),
         height: ScreenUtil().setHeight(200),
         color: Colors.red,
         child: Text(
          '我的宽度:${ScreenUtil().setWidth(375)}dp',
          style: TextStyle(
           color: Colors.white,
           fontSize: ScreenUtil().setSp(12, false),
          ),
         ),
        ),
        Container(
         width: ScreenUtil().setWidth(375),
         height: ScreenUtil().setHeight(200),
         color: Colors.blue,
         child: Text('我的宽度:${ScreenUtil().setWidth(375)}dp',
           style: TextStyle(
            color: Colors.white,
            fontSize: ScreenUtil().setSp(12, false),
           )),
        ),
       ],
      ),
      Text('设备宽度:${ScreenUtil.screenWidth}px'),
      Text('设备高度:${ScreenUtil.screenHeight}px'),
      Text('设备的像素密度:${ScreenUtil.pixelRatio}'),
      Text('底部安全区距离:${ScreenUtil.bottomBarHeight}px'),
      Text('状态栏高度:${ScreenUtil.statusBarHeight}px'),
      Text(
       '实际高度的dp与设计稿px的比例:${ScreenUtil().scaleHeight}',
       textAlign: TextAlign.center,
      ),
      Text(
       '实际高度的dp与设计稿px的比例:${ScreenUtil().scaleHeight}',
       textAlign: TextAlign.center,
      ),
      Text(
       '宽度和字体相对于设计稿放大的比例:${ScreenUtil().scaleWidth * ScreenUtil.pixelRatio}',
       textAlign: TextAlign.center,
      ),
      Text(
       '高度相对于设计稿放大的比例:${ScreenUtil().scaleHeight * ScreenUtil.pixelRatio}',
       textAlign: TextAlign.center,
      ),
      SizedBox(
       height: ScreenUtil().setHeight(100),
      ),
      Text('系统的字体缩放比例:${ScreenUtil.textScaleFactory}'),
      Column(
       crossAxisAlignment: CrossAxisAlignment.start,
       children: [
        Text('我的文字大小在设计稿上是14px，不会随着系统的文字缩放比例变化',
          style: TextStyle(
            color: Colors.black,
            fontSize: ScreenUtil().setSp(14, false))),
        Text('我的文字大小在设计稿上是14px，会随着系统的文字缩放比例变化',
          style: TextStyle(
            color: Colors.black, fontSize: ScreenUtil().setSp(14))),
       ],
      )
     ],
    ),
   ),
  );
 }

import 'dart:ui';
//因为window是dart:ui中提供的,所以需要引入这个包.
window.physicalSize //Size(1080.0, 1794.0) 单位px
width = window.physicalSize.width //宽度
height = window.physicalSize.height //高度

//使用这个方法则无需引入包
MediaQuery.of(context).size  //Size(411.4, 683.4)  单位:dp
widhtDp = MediaQuery.of(context).size.width  //宽度 411.4
heightDp = MediaQuery.of(context).size.height //高度 683.4

scaleWidth = width / 1080;
scaleHeight = height / 1920;

MediaQuery.of(context).devicePixelRatio
window.physicalSize   

import ‘dart:ui';

scaleWidth = widhtDp / 360;
scaleHeight = heightDp / 640;